Piping structure with inner heat exchanger and refrigeration cycle device having the same

ABSTRACT

A piping structure for a refrigerant cycle device includes an inner heat exchanger, and a bypass pipe through which refrigerant flows while bypassing the inner heat exchanger. The inner heat exchanger has a first flow passage in which high-pressure refrigerant before being decompressed flows and a second flow passage in which low-pressure refrigerant after being decompressed flows. The refrigerant cycle device includes plural low-pressure side heat exchangers, and the plural low-pressure side heat exchangers are located such that refrigerant from a part of the low-pressure side heat exchangers flows through the second flow passage of the inner heat exchanger, and refrigerant from the other part of the low-pressure side heat exchangers flows through the bypass pipe while bypassing the inner heat exchanger.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-124740 filed on Apr. 28, 2006, the contents of which are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piping structure with an inner heat exchanger and a refrigeration cycle device provided with the same.

2. Description of the Related Art

Piping for a refrigeration cycle device for a vehicle air conditioner has been known as a piping structure provided with an inner heat exchanger. This piping for a refrigeration cycle device has a double pipe structure as an inner heat exchanger, as described in JP-A-2001-277842 (corresponding to U.S. Pat. No. 6,866,090), for example. The double pipe structure has a high-pressure refrigerant pipe extending from a compressor to an evaporator via a condenser and a low-pressure refrigerant pipe extending from the evaporator to the compressor, and is constructed in such a way that one of the high-pressure refrigerant pipe and the low-pressure refrigerant pipe is inserted into the other one at least in a part of them.

With this, in the double pipe structure, heat can be exchanged between high-temperature and high-pressure refrigerant and low-temperature and low-pressure refrigerant, and the high-pressure refrigerant flowing out of the condenser is super-cooled by the low-pressure refrigerant, so as to increase an amount of liquid refrigerant to be supplied to the evaporator. In the evaporator, as the amount of liquid refrigerant increases, the resistance to flow of the refrigerant decreases and a cooling capacity in the evaporator increases. Furthermore, the low-pressure refrigerant flowing out of the evaporator is super-heated by the high-pressure refrigerant so as to prevent liquid refrigerant from being compressed in the compressor.

However, in an air conditioner for a vehicle (dual air conditioner) provided with the plural evaporators, for example, for a front seat and a rear seat, when a low-pressure refrigerant pipe from each of the evaporators is made to communicate with a low-pressure refrigerant pipe of a double pipe part, there is presented a problem that a pressure loss in the low-pressure refrigerant pipe of the double pipe part increases depending on the shape of the double pipe part thereby decreasing a cooling capacity.

SUMMARY OF THE INVENTION

In view of the foregoing problems, it is an object of the present invention to provide a piping structure and a refrigeration cycle device, which can reduce a pressure loss of refrigerant in a low-pressure refrigerant pipe.

It is another object of the present invention to provide a refrigeration cycle device which can increase cooling capacity by reducing pressure loss of low-pressure refrigerant.

According to an example of the present invention, a piping structure is for a refrigerant cycle device that includes a compressor for compressing refrigerant, a high-pressure side heat exchanger for cooling high-pressure refrigerant discharged from the compressor, a decompression unit for decompressing the high-pressure refrigerant from the high-pressure side heat exchanger, and first and second low-pressure side heat exchangers for evaporating low-pressure refrigerant decompressed in the decompression unit. The piping structure includes an inner heat exchanger, and a bypass pipe that defines a bypass flow passage through which the low-pressure refrigerant flows while bypassing the inner heat exchanger. The inner heat exchanger has a first flow passage in which high-pressure refrigerant before being decompressed flows and a second flow passage in which low-pressure refrigerant after being decompressed by the decompression unit flows, and the first and second flow passages are provided to exchange heat between the high-pressure refrigerant and the low-pressure refrigerant. Furthermore, the first flow passage includes a first inlet-side connection part connected to a refrigerant outflow side of the high-pressure side heat exchanger on its one end side and a first outlet-side connection part connected to a refrigerant inflow side of the decompression unit on its other end side, and the second flow passage includes a second inlet-side connection part connected to a refrigerant outflow side of the first low-pressure side heat exchanger on its one end side and a second outlet-side connection part connected to a refrigerant suction side of the compressor on its other end side. In addition, the bypass flow passage includes a bypass inlet-side connection part connected to a refrigerant outflow side of the second low-pressure side heat exchanger on its one end side and is joined to the second outlet-side connection part on its other end side. Therefore, it is possible to reduce a pressure loss in a low-pressure refrigerant pipe, thereby preventing a reduce of cooling capacity due to a pressure loss increase.

For example, the first outlet-side connection part may include two outlet-side connection portions which are connected respectively to first and second decompression portions of the decompression unit. Alternatively, the inner heat exchanger may be a double pipe part in which an inside pipe is passed through an outside pipe. In this case, one of the first flow passage and the second flow passage is a flow passage between the outside pipe and the inside pipe, and another one thereof is a flow passage within the inside pipe.

According to another example of the present invention, a piping structure for a refrigerant cycle device includes an inner heat exchanger and a bypass pipe that defines a bypass flow passage through which a part of the low-pressure refrigerant flows while bypassing the inner heat exchanger. The inner heat exchanger has a first flow passage in which high-pressure refrigerant before being decompressed flows and a second flow passage in which low-pressure refrigerant after being decompressed flows, and the first and second flow passages are provided to exchange heat between the high-pressure refrigerant and the low-pressure refrigerant. Therefore, pressure loss in the low-pressure side can be effectively reduced, thereby improving cooling capacity.

According to another example of the present invention, a refrigeration cycle device includes: a compressor for compressing refrigerant; a high-pressure side heat exchanger for cooling high-pressure refrigerant discharged from the compressor; a plurality of decompression units and low-pressure side heat exchangers, an inner heat exchanger and a bypass pipe. The decompression units are located to decompress the high-pressure refrigerant to be low-pressure refrigerant, and the low-pressure side heat exchangers are located respectively downstream from the decompression units to evaporate the low-pressure refrigerant from the decompression units. The inner heat exchanger has a first flow passage in which high-pressure refrigerant before being decompressed flows and a second flow passage in which low-pressure refrigerant after being decompressed flows, and the first and second flow passages are provided to exchange heat between the high-pressure refrigerant and the low-pressure refrigerant. The bypass pipe defines a bypass flow passage through which the low-pressure refrigerant bypasses the inner heat exchanger, and the plurality of low-pressure side heat exchangers include at least a first low-pressure side heat exchanger and a second low-pressure side heat exchanger.

In the inner heat exchanger, the first flow passage includes a first inlet-side connection part connected to a refrigerant outflow side of the high-pressure side heat exchanger on its one end side, and a first outlet-side connection part connected to a refrigerant inflow side of the decompression units on its other end side. Furthermore, the second flow passage includes a second inlet-side connection part connected to a refrigerant outflow side of the first low-pressure side heat exchanger on its one end side, and a second outlet-side connection part connected to a refrigerant suction side of the compressor on its other end side. In addition, the bypass flow passage includes a bypass inlet-side connection part connected to a refrigerant outflow side of the second low-pressure side heat exchanger on its one end side, and is joined to the second outlet-side connection part on its other end side. Accordingly, it is possible for the low-pressure refrigerant to bypass the inner heat exchanger through the bypass flow passage, thereby reducing pressure loss in the low-pressure refrigerant and improving the cooling capacity.

For example, the plurality of low-pressure side heat exchangers may further include a third low-pressure side heat exchanger. In this case, a refrigerant outflow side of the third low-pressure side heat exchanger may be connected to the bypass inlet-side connection part. Alternatively, a refrigerant outflow side of the third low-pressure side heat exchanger may be connected to the second inlet-side connection part of the second flow passage of the inner heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings.

FIG. 1 is a schematic diagram showing an air conditioner for a vehicle in a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a piping structure with an inner heat exchanger in the first embodiment.

FIG. 3 is a perspective view showing the whole of the piping structure with an inner heat exchanger in the first embodiment.

FIG. 4 is a cross-sectional view showing the portion IV in FIG. 3.

FIG. 5 is a schematic diagram showing a refrigeration cycle device in the first embodiment.

FIG. 6 is a graph showing a Mollier diagram of a refrigeration cycle device.

FIG. 7 is a graph showing the relationship between a total bending angle of a double pipe part, and a cooling capacity.

FIG. 8 is a graph showing the relationships between an amount of heat exchange, a pressure loss and a cooling capacity, and the length of the double pipe part.

FIG. 9 is a schematic diagram showing a refrigeration cycle device in a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

In this embodiment, a piping structure 170 with an inner heat exchanger in accordance with the present invention and a refrigeration cycle device 100A using the same are typically used for an air conditioner for a vehicle (hereinafter referred to as air conditioner) 100.

As shown in FIG. 1, a vehicle is partitioned by a dash panel 3 into an engine room 1 in which an engine 10 for a vehicle running is mounted and a vehicle compartment 2 for occupants. Among a refrigeration cycle device 100A and interior units 100B, 100C which construct the air conditioner 100, a part of the refrigeration cycle device 100A (except for expansion valves 131, 132, and evaporators 141, 142 as low-pressure side heat exchangers) is disposed in the engine room 1. The air conditioner 100 in this embodiment is a dual air conditioner provided with two interior units 100B, 100C for the front seat and the rear seat of the vehicle. The interior unit 100B for the front seat is disposed in an instrument panel of the vehicle compartment 2 and the interior unit 100C for the rear seat is disposed between the rear side body of the vehicle compartment 2 and an interior panel.

The interior unit 100B for the front seat is a unit in which a blower 102, the evaporator 141, and a heater core 103 are disposed in an air-conditioner case 101. The blower 102 selectively sucks outside air (i.e., air outside the vehicle compartment) or/and inside air (i.e., air inside the vehicle compartment) and blows the sucked air to the evaporator 141 and the heater core 103. The evaporator 141 is a cooling heat exchanger that evaporates in itself refrigerant associated with the operation of the refrigeration cycle device 100A to be described later to cool air by evaporative latent heat. The heater core 103 is a heat exchanger for heating that heats the air by using hot water (engine-cooling water) from an engine 10 as a heating source.

An air mix door 104 is disposed in the air conditioner case 101 near the heater core 103, and the mixing ratio between the air cooled by the evaporator 141 and the air heated by the heater core 103 is changed according to an opening degree of the air mix door 104 so as to control a vehicle compartment temperature to a set temperature that is set by the occupant.

On the other hand, the interior unit 100C for the rear seat is a unit in which a blower 109 and the evaporator 142 are disposed in an air conditioner case 108. The blower 109 takes inside air (i.e., air inside the vehicle compartment) and blows the air-conditioning air to the evaporator 142. The evaporator 142 is a heat exchanger for cooling that evaporates in itself refrigerant associated with the operation of the refrigeration cycle device 100A to be described later to cool the air by evaporative latent heat at that time. In this embodiment, the interior unit 100C for the rear seat is not provided with the heater core 103 and the air mix door 104 which are provided in the interior unit 100B for the front seat.

The refrigeration cycle device 100A is provided with a compressor 110, a condenser 120 as a high-pressure side heat exchanger, expansion valves 131, 132, and the evaporators 141, 142. These parts are connected to each other by piping 150 to form a closed circuit. The piping structure 170 with an inner heat exchanger of this embodiment of the present invention is disposed in a part of the piping 150. The condenser 120 is a high-pressure side heat exchanger and is also called a radiator or a gas cooler. The evaporators 141, 142 are low-pressure side heat exchangers and are also called coolers or heat absorbers. The expansion valves 131, 132 are pressure reducers and can be provided as throttles, valves, or ejectors. In the refrigeration cycle device 100A of this embodiment, HFC134a is used as refrigerant, as an example.

The compressor 110 is a fluid machine for compressing refrigerant in the refrigeration cycle device 100A to a state of high temperature and high pressure and is driven here by the driving force of the engine 10. That is, a pulley 111 is fixed to the driving shaft of the compressor 110 and the driving force of the engine 10 is transmitted to the pulley 111 via a crank pulley 11 and a driving belt 12, thereby the compressor 110 is driven by the driving force. The pulley 111 is provided with a magnetic clutch (not shown) for connecting or disconnecting the driving shaft of the compressor to or from the pulley 111. The condenser 120 is a heat exchanger connected to the discharge side of the compressor 110 and for condensing and liquefying refrigerant by exchanging heat between the refrigerant and the outside air.

The expansion valve (hereinafter referred to as front expansion valve) 131 and the expansion valve (hereinafter referred to as rear expansion valve) 132 are valves for reducing the pressure of liquid-phase refrigerant flowing out of the condenser 120 to expand the refrigerant, that is, for isentropically reducing the pressure of liquid-phase refrigerant. The expansion valve 131 and the expansion valve 132 are disposed on the interior units 100B, 100C so as to be in contact with the evaporators 141, 142. The expansion valves 131, 132 are temperature type expansion valves each of which controls the degree of opening of throttle so as to make the degree of superheating of refrigerant flowing out of the evaporators 141, 142 (refrigerant to be sucked to the compressor 110) at a specified value. The evaporators 141, 142, as described above, are cooling heat exchangers for cooling air, and the refrigerant outlet sides of the evaporators 141, 142 are connected to the suction side of the compressor 110.

The piping structure 170 with the inner heat exchanger, as shown in FIG. 2, has a double pipe part 160 and a bypass pipe 171. The double pipe part 160 forms a double pipe structure at least in the high-pressure piping 151 through which high-temperature, high-pressure refrigerant from the compressor 110 flows and in the low-pressure piping 152 through which low-temperature, low-pressure refrigerant flows from the evaporator 141 of the air-conditioning unit 100B for the front seat (hereinafter referred to as front evaporator) toward the compressor 110, among the piping 150.

The bypass pipe 171 forms a portion of the low-pressure piping 152 through which low-temperature, low-pressure refrigerant from the compressor 110 flows from the rear evaporator 142 of the air-conditioning unit 100C for the rear seat toward the compressor 110, in the piping 150. With this, the low-pressure refrigerant from the rear evaporator 142 bypasses the double pipe part (heat exchanger) 160 and flows to the compressor 110.

The piping structure 170 with the inner heat exchanger will be described below in detail with reference to FIG. 3 and FIG. 4. FIG. 3 is the external view of the piping structure 170 with the inner heat exchanger and FIG. 4 is a cross-sectional view showing the portion IV in FIG. 3. The double pipe part 160 has a total length (length between a point A and a point B in FIG. 3) of approximately 600 mm and is constructed with a straight portion 163 a extending straightly and a plurality of bending portions 163 b (e.g., two bending portions in this embodiment) so as to avoid the interference with the engine 10 and the other parts such as a vehicle body and is mounted in the engine room 1. Here, the angle of the bending portion 163 b is an angle with respect to the straight pipe portion 163 a (angles α, β in FIG. 3) and the total sum of the angles of the respective bending portions 163 b is defined as the total bending angle (angle (α+β) in FIG. 3). The total bending angle of the double pipe part 160 in this embodiment is approximately 160 degrees.

The double pipe part 160 has an outside pipe (corresponding to outside piping) 161 and an inside pipe (corresponding to inside piping) 162, which are formed individually, and the inside pipe 162 is passed through the outside pipe 161. The outside pipe 161 is, for example, an aluminum pipe having a diameter of 22 mm and the inside side pipe 162 is, for example, an aluminum pipe having a diameter of 19.1 mm. The outside pipe 161 is combined with the inside pipe 162 and then has the whole periphery of its end portion contracted in diameter inwardly in the radial direction side and welded to the circumferential surface of the inside pipe 162 air-tightly or liquid-tightly. Thus, a space is formed between the outside pipe 161 and the inside pipe 162, and is used as a flow passage 160 a between the inside and outside pipes 161, 162.

Liquid piping 164, 165, which make the outside communicate with the flow passage 160 a between the inside and outside pipes 161, 162 and are made of aluminum and form a part of the high-pressure piping 151, are brazed to the circumferential wall surface on both end portions (the points A, B in FIG. 3) of the outside pipe 161. The liquid piping 164 has at least one or more bending portion and extends to the condenser 120 and has a joint 164 b as a connection portion disposed at its tip. The liquid piping 165 has at least one or more bending portion and extends to the front expansion valve 131 and has a joint 165 b disposed at its tip.

Further, the liquid piping 165 branches at a middle point in the longitudinal direction (middle point shown by C in FIG. 3 in this embodiment) and has aluminum liquid piping 168 connected thereto by the use of a three-way branch connector 169. The liquid piping 168 has at least one or more bending portion and extends to the rear expansion valve 132 and has a joint 168 b disposed at its tip. The joint 164 b is connected to the outflow side of refrigerant of the condenser 120 and the joint 165 b is connected to the inflow side of refrigerant of the front expansion valve 131 and the joint 168 b is connected to the inflow side of refrigerant of the rear expansion valve 132. With this, high-pressure refrigerant flows through the liquid piping 164, the flow passage 160 a between the inside and outside pipes 161, 162, the liquid piping 165, and the liquid piping 168.

On the other hand, the inside pipe 162 has suction piping 166, which is made of aluminum and forms a part of the low-pressure piping 152, disposed at its end on the liquid piping 165 side. The suction piping 166 has a joint 166 a disposed at its end. The inside pipe 162 has a joint 167 a disposed at its end on the liquid piping 164 side.

Moreover, the bypass pipe 171 communicating with the interior of the inside pipe 162 is connected to a point between the welding point of the outside pipe 161 and the joint 167 a in the end portion of the inside pipe 162 (middle point shown by D in FIG. 3 in this embodiment). The bypass pipe 171 is, for example, a pipe made of aluminum and having a diameter 12.7 mm and is connected by brazing to the inside pipe 162 in the shape of a letter T. The bypass pipe 171 has at least one or more bending portion and extending to the rear evaporator 142 and has a joint 171 a disposed at its tip.

The joint 166 a is connected to the outflow side of refrigerant of the front evaporator 141, the joint 167 a is connected to the inflow side of refrigerant of the compressor 110 and the joint 171 a is connected to the outflow side of the rear evaporator 142. With this, low-pressure refrigerant flows through the suction piping 166, the bypass pipe 171, and the inside pipe 162.

Circumferential grooves 162 c and a spiral groove 162 a are formed on the surface of the inside pipe 162 corresponding to a region in which the flow passage 160 a between the inside and outside pipes 161, 162 is formed. The circumferential grooves 162 c are grooves formed in correspondence with positions in which the respective liquid piping 164, 165 are connected to the outside pipe 161 and extending in the circumferential direction of the inside pipe 162. The spiral groove 162 a is a multiple groove connected to the respective circumferential grooves 162 c and extending in the spiral shape in the longitudinal direction of the inside pipe 162 between the circumferential grooves 162 c. Ridge portions 162 b which substantially hold the outside diameter of the inside pipe 162 (actually, is contracted in diameter) are formed between the spiral grooves 162 a. The circumferential grooves 162 c and the spiral groove 162 a correspond to the groove portions in the present invention, and expand the flow passage 160 a between the inside and outside pipes 161, 162 and increase the surface area of the inside pipe 162 to improve the heat exchange efficiency between the high-pressure refrigerant and the low-pressure refrigerant. The circumferential grooves 162 c and the spiral groove 162 a can be formed by a grooving tool, for example.

The flow passage 160 a between the inside and outside pipes 161, 162 in this embodiment corresponds to a first flow passage of the inner heat exchanger, and the inside pipe 162 corresponds to a second flow passage of the inner heat exchanger. The joint 164 b corresponds to a first inlet side connection part in the piping structure 170. The joint 165 b corresponds to a first outlet side connection portion in the piping structure 170. The joint 168 b corresponds to a first outlet side connection part in the piping structure 170. The joint 166 a corresponds to a second inlet side connection part in the piping structure 170. The joint 167 a corresponds to a second outlet side connection part in the piping structure 170. The joint 171 a corresponds to a bypass inlet side connection part in the piping structure 170.

A joint unit as a connection part in this embodiment means a unit that an operator can fix or unfix such as a joint unit to be fastened by bolts or nuts and a quick joint unit having engaging claws. The joint units in this embodiment are units for connecting flow passages without requiring a connection work involving high temperature or flame such as brazing and welding. The joint units used at positions shown in this embodiment fix, unfix, and replace commercially available piping structure 170. In this embodiment, piping parts including the inner heat exchanger and the bypass pipe are provided as one part, so the bypass pipe 171 is jointed to the inside pipe 162 by a connection work using flame such as brazing. However, the bypass pipe 171 may be connected to the inside pipe 162 by a detachable/attachable joint unit such as a bolt or a nut.

Next, the operation and effect based on the above-mentioned construction will be described with reference to FIG. 5 and FIG. 6. FIG. 5 is a schematic view showing the construction of the refrigeration cycle device 100A and FIG. 6 is a Mollier diagram showing a super-cooled state and a super-heated state in the double pipe part 160.

When the occupant makes a request for air conditioning, for example, a cooling operation, the compressor 110 has its electromagnetic clutch connected, thereby being driven by the engine 10. In this case, the compressor 110 sucks refrigerant from the evaporators 141, 142 and compresses the refrigerant and then discharges the refrigerant as high-temperature, high-pressure refrigerant to the condenser 120 (refrigerant radiator). The high-pressure refrigerant is cooled, condensed, and liquefied by the condenser 120. The refrigerant is brought to a substantially liquid phase at the refrigerant outlet of the condenser 120.

The condensed and liquefied refrigerant flows from the liquid piping 164 through the flow passage 160 a between the inside and outside pipes and the liquid piping 165 and reaches the front expansion valve 131. Then, the refrigerant branches at the point C in the liquid piping 165 and flows through the liquid piping 168 and reaches the rear expansion valve 132. The refrigerant is reduced in pressure in the expansion valves 131, 132, thereby being expanded and decompressed, and is evaporated in the evaporators 141, 142. In the evaporators 141, 142, the air passing therethrough is cooled by the evaporation of the refrigerant.

The saturated gas refrigerant evaporated in the front evaporator 141 flows as low-temperature refrigerant through the suction piping 166 and inside pipe 162 of the double pipe part 160 and returns to the compressor 110. On the other hand, the saturated gas refrigerant from the rear evaporator 142 flows through the bypass pipe 171 and is joined with the inside pipe 162 at the point D and returns to the compressor 110. In this manner, the saturated gas refrigerant from the rear evaporator 142 bypasses the double pipe part (inner heat exchanger) 160.

Here, in the double pipe part 160, heat is exchanged between the high-pressure refrigerant and the low-pressure refrigerant, thereby the high-pressure refrigerant is cooled and the low-pressure refrigerant is heated. That is, the liquid-phase refrigerant flowing out of the condenser 120 is further super-cooled by the double pipe part 160, thereby being increasingly brought to lower temperature. Moreover, the saturated gas refrigerant flowing out of the front evaporator 141 is further heated by the double pipe part 160, thereby being brought to super-heated gas refrigerant.

As described above, in this embodiment, of the low-pressure refrigerant from the front and rear evaporators 141, 142 to the compressor 110, only the low-pressure refrigerant from the front evaporator 141 is made to flow through the double pipe part (inner heat exchanger) 160 and low-pressure refrigerant from the rear evaporator 142 is made to bypass the double pipe part 160 to flow to the compressor 110 through the bypass pipe 171. Thus, as compared with a case in which the low-pressure refrigerant from both of the evaporators 141, 142 is made to flow through the double pipe part 160, it is possible to prevent an increase in pressure loss in the low-pressure piping 152 and in the inside pipe 162 and hence to prevent a decrease in cooling capacity in the refrigeration cycle device 100A. Moreover, it is possible to decrease also the amount of heat exchange in the double pipe part 160 and hence to prevent an increase in temperature in the low-pressure refrigerant. Thus, it is possible to prevent an increase in inside temperature and discharge temperature in the compressor 110 and hence to prevent such a decrease in durability of the parts of the compressor 110 that is caused by heat.

For example, according to experiments by the inventors, in a case where the flow rate of the low-pressure refrigerant from the front evaporator 141 is 100 kg/h and the flow rate of the low-pressure refrigerant from the rear evaporator 142 is 50 kg/h, when the low-pressure refrigerant from both the front evaporator 141 and the rear evaporator 142 is made to flow through the double pipe part 160, a pressure loss in the double pipe part 160 is 30 kPa and the amount of heat exchange is 800 w and a discharge temperature in the compressor 110 is 105 degrees. In contrast, when the low-pressure refrigerant from the rear evaporator 142 is made to bypass the double pipe part 160, a pressure loss in the double pipe part 160 is decreased to 20 kPa and the amount of heat exchange is decreased to 600 w and a discharge temperature in the compressor 110 is decreased to 100 degrees.

The total bending angle of the double pipe part 160 in this embodiment is approximately 160 degrees. However, when the total bending angle of the double pipe part 160 is not less than 160 degrees as shown in FIG. 7, the piping structure 170 with the inner heat exchanger of the present invention is employed to make low-pressure refrigerant from the rear evaporator 142 bypass the double pipe part 160. With this, it is possible to improve a cooling capacity as compared with a case in which low-pressure refrigerant from the rear evaporator 142 does not bypass the double pipe part 160. Moreover, when the total bending angle of the double pipe part 160 is comparatively large, the straight distance between the point A and the point B of the double pipe part 160 becomes short and hence the length of the pipe 171 bypassing the double pipe part 160 can be made shorter. Thus, it is possible to easily arrange the bypass pipe 171 in the engine room 1. In FIGS. 7 and 8, Gr=210 Kg/h shows a refrigerant flow rate when the low-pressure refrigerant from the rear evaporator 142 passes the double pipe part 160 and Gr=150 Kg/h shows a refrigerant flow rate in the double pipe part 160 when the low-pressure refrigerant from the rear evaporator 142 bypasses the double pipe part 160.

FIG. 8 is a graph showing the relationship between the length of the double pipe part 160, and the amount of heat exchange in the double pipe part 160, a pressure loss in the low-pressure piping 152, a pressure loss in the inside pipe 162, and the cooling capacity of the refrigeration cycle device 100A by comparing a construction in which low-pressure refrigerant from the rear evaporator 142 bypasses the double pipe part 160 (bypass double pipe part) with a construction in which low-pressure refrigerant from the rear evaporator 142 does not bypass the double pipe part 160 (pass double pipe part). According to this, it can be found that as the length of the double pipe part 160 becomes longer, the cooling capacity becomes lower from a point close to 600 mm because of an increase in pressure loss. While the length of the double pipe part 160 is 600 mm in this embodiment, when the length of the double pipe length is comparatively long and is 600 mm or more, it is possible to prevent the pressure loss and to reduce a decrease in cooling capacity by employing the piping structure 170 with the inner heat exchanger of the present invention to make low-pressure refrigerant bypass the double pipe part 160.

In this embodiment, the high-pressure refrigerant flows through the flow passage 160 a between the inside and outside pipes 161, 162 and the low-pressure refrigerant flows through the inside pipe 162, so the inside pipe 162 through which the low-pressure refrigerant flows is covered with the outside pipe 161. For this reason, it can prevent heat radiated from the engine 10 and the like from being received by the low-pressure refrigerant in the inside pipe 162.

Second Embodiment

A second embodiment of the present invention will be described with reference to FIG. 9. In the above-described first embodiment, the piping structure 170 with the inner heat exchanger is applied to the refrigeration cycle device 100A of the dual air conditioner 100 that are provided with the two evaporators 141, 142 for the front seat and the rear seat. In contrast to this, in this embodiment, the piping structure 170 with the inner heat exchanger of the present invention is applied to a refrigeration cycle device 200A of an air conditioner for a vehicle (triple air conditioner) provided with three evaporators 141, 142, and 243 for the front seat, the rear seat, and a cool box.

The piping structure 170 with the inner heat exchanger in this embodiment has the same construction as in the first embodiment shown in FIG. 2 to FIG. 4, and the condenser 120, the compressor 110, the front expansion valve 131, the front evaporator 141 are connected to the joints 164 b, 167 a, 165 b, and the 166 a, respectively. Piping 250 forming the high-pressure piping 151 extending to the rear expansion valve 132 is connected to the joint 168 b at the tip of the liquid piping 168 and this piping 250 branches at a point E shown in FIG. 9, and the branching piping 251 is connected to an expansion valve 233 and an evaporator 243 for a cool box. With this, high-pressure refrigerant flowing out of the liquid piping 168 flows through the piping 250, 251 and reaches the rear expansion valve 132 and the expansion valve 233 on the evaporator 243 side for the cool box.

Moreover, piping 253 forming the low-pressure piping 152 from the rear evaporator 142 is connected to the joint 171 a at the tip of the bypass pipe 171. Piping 254 forming the low-pressure piping 152 from the evaporator 243 for the cool box is joined to the piping 253 at a point F shown in FIG. 9. With this, low-pressure refrigerant from the rear evaporator 142 and the evaporator 243 for the cool box flows into the bypass pipe 171. The other construction of the air conditioner for a vehicle in this embodiment may be the same as in the first embodiment.

In the case of the air conditioner for a vehicle provided with three evaporators 141, 142, and 143 like this embodiment, when the entire low-pressure refrigerant from the three evaporators 141, 142, and 143 is made to flow through the double pipe part 160, a pressure loss in the low-pressure piping 152 increases to decrease a cooling capacity. In this embodiment, among the low-pressure refrigerant flowing from the respective evaporators 141, 142, and 143 for the front seat, the rear seat, and the cool box to the compressor 110, only the low-pressure refrigerant from the front evaporator 141 is made to flow through the double pipe part (heat exchanger) 160 and the low-pressure refrigerant from the rear evaporator 142 and the evaporator 243 for the cool box is made to bypass the double pipe part 160 to flow to the compressor 110. With this, it is possible to prevent an increase in pressure loss in the low-pressure piping 152 and hence to prevent a decrease in cooling capacity. Moreover, the amount of heat exchange in the double pipe part 160 also decreases. Accordingly, it is possible to prevent an increase in internal temperature and discharge temperature in the compressor 110 and hence to prevent such a decrease in durability of the parts of the compressor 110 that is caused by heat.

Other Embodiments

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

For example, in the second embodiment described above, the low-pressure refrigerant from the front evaporator 141 is made to flow through the double pipe part 160 and the low-pressure refrigerant from the rear evaporator 142 and the evaporator 243 for the cool box is made to bypass the double pipe part 160. However, the construction is not limited to this but, for example, the low-pressure refrigerant from the front evaporator 141 and the evaporator 243 for the cool box may be made to flow through the double pipe part 160 and only the low-pressure refrigerant from the rear evaporator 142 may be made to bypass the double pipe part 160.

The spiral groove 162 a of the inside pipe 162 in the respective embodiments is not limited to this construction, but it is only necessary that the spiral groove 162 a can improve heat exchange efficiency between high-pressure refrigerant and low-pressure refrigerant and hence, for example, a straight groove extending in the longitudinal direction of the inside pipe 162 may be employed in place of the spiral groove 162 a.

In the above embodiments, the outside pipe 161, the inside pipe 162 and the bypass pipe 171 are made of aluminum, but may be made of iron or copper. Moreover, the double pipe part 160 has the construction including the outside pipe 161 and the inside pipe 162 which are formed separately from each other. However, in place of this construction, the double pipe part 160 may be formed of an extruded double pipe in which the outside pipe 161 and the inside pipe 162 are formed at the same time by extrusion so as to have a connection portion.

The inner heat exchanger 160 is constructed as the double pipe including the outside pipe 161 and the inside pipe 162 in the above respective embodiments, but may be constructed of parallel pipes.

Moreover, in place of this construction, the liquid piping 164, 165, 168, and the bypass pipe 171 may be straight pipes when the straight pipes do not have a bad effect in a combination with the mating parts.

In the above respective embodiments, the piping structure 170 with the inner heat exchange of the present invention is applied to the air conditioner for a vehicle 100, but may be applied to a household air conditioner. When the inner heat exchanger is constructed as the double pipe part 160 in the household air conditioner, the double pipe part 160 can be used under the conditions that the outside atmospheric temperature of the outside pipe 161 is lower than in the case of the engine room 1 in which the double pipe part 160 is used for a vehicle. Thus, depending on the performance of heat exchange between the high-pressure refrigerant and the low-pressure refrigerant, the low-pressure refrigerant may be made to flow through the flow passage 160 a between the inside and outside pipes 161, 162 and the high-pressure refrigerant may be made to flow through the inside pipe 162.

The piping in this embodiment can be applied also to a supercritical-pressure refrigeration cycle device using carbon dioxide, for example, as refrigerant. In the supercritical-pressure refrigeration cycle device, a high-pressure side heat exchanger is used as a refrigerant radiator and the expansion valve is used as a pressure control valve for reducing the refrigerant pressure.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims. 

1. A piping structure for a refrigerant cycle device that includes a compressor for compressing refrigerant, a high-pressure side heat exchanger for cooling high-pressure refrigerant discharged from the compressor, a decompression unit for decompressing the high-pressure refrigerant from the high-pressure side heat exchanger, and first and second low-pressure side heat exchangers for evaporating low-pressure refrigerant decompressed in the decompression unit, the piping structure comprising: an inner heat exchanger that has a first flow passage in which high-pressure refrigerant before being decompressed flows and a second flow passage in which low-pressure refrigerant after being decompressed by the decompression unit flows, the first and second flow passages being provided to exchange heat between the high-pressure refrigerant and the low-pressure refrigerant; and a bypass pipe that defines a bypass flow passage through which the low-pressure refrigerant bypasses the inner heat exchanger, wherein the first flow passage includes a first inlet-side connection part connected to a refrigerant outflow side of the high-pressure side heat exchanger on its one end side, and a first outlet-side connection part connected to a refrigerant inflow side of the decompression unit on its other end side, wherein the second flow passage includes a second inlet-side connection part connected to a refrigerant outflow side of the first low-pressure side heat exchanger on its one end side and a second outlet-side connection part connected to a refrigerant suction side of the compressor on its other end side, and wherein the bypass flow passage includes a bypass inlet-side connection part connected to a refrigerant outflow side of the second low-pressure side heat exchanger on its one end side and is joined to the second outlet-side connection part on its other end side.
 2. The piping structure according to claim 1, wherein the first outlet-side connection part includes two outlet-side connection portions which are connected respectively to first and second decompression portions of the decompression unit.
 3. The piping structure according to claim 1, wherein the inner heat exchanger is a double pipe part in which an inside pipe is passed through an outside pipe, and wherein one of the first flow passage and the second flow passage is a flow passage between the outside pipe and the inside pipe, and another one thereof is a flow passage within the inside pipe.
 4. The piping structure according to claim 3, wherein the double pipe part includes one or more bending portion, and wherein a total bending angle of totalizing a bending angle of the bending portion is 160 degrees or more.
 5. The piping structure according to claim 3, wherein the double pipe part has a length of 600 mm or more.
 6. The piping structure according to claim 3, wherein the first flow passage is a flow passage between the outside pipe and the inside pipe, and wherein the second flow passage is a flow passage within the inside pipe.
 7. The piping structure according to claim 3, wherein the double pipe part has a groove provided on an outer surface of the inside pipe.
 8. A refrigeration cycle device comprising: a compressor for compressing refrigerant; a high-pressure side heat exchanger for cooling high-pressure refrigerant discharged from the compressor; a plurality of decompression units and low-pressure side heat exchangers, wherein the decompression units are located to decompress the high-pressure refrigerant to be low-pressure refrigerant, and the low-pressure side heat exchangers are located respectively downstream from the decompression units to evaporate the low-pressure refrigerant from the decompression units; an inner heat exchanger that has a first flow passage in which high-pressure refrigerant before being decompressed flows and a second flow passage in which low-pressure refrigerant after being decompressed flows, the first and second flow passages being provided to exchange heat between the high-pressure refrigerant and the low-pressure refrigerant; and a bypass pipe that defines a bypass flow passage through which the low-pressure refrigerant bypasses the inner heat exchanger, wherein the first flow passage includes a first inlet-side connection part connected to a refrigerant outflow side of the high-pressure side heat exchanger on its one end side, and a first outlet-side connection part connected to a refrigerant inflow side of the decompression units on its other end side, wherein the plurality of low-pressure side heat exchangers include at least a first low-pressure side heat exchanger and a second low-pressure side heat exchanger, wherein the second flow passage includes a second inlet-side connection part connected to a refrigerant outflow side of the first low-pressure side heat exchanger on its one end side, and a second outlet-side connection part connected to a refrigerant suction side of the compressor on its other end side, and wherein the bypass flow passage includes a bypass inlet-side connection part connected to a refrigerant outflow side of the second low-pressure side heat exchanger on its one end side, and is joined to the second outlet-side connection part on its other end side.
 9. The refrigeration cycle device according to claim 8, wherein the plurality of low-pressure side heat exchangers further include a third low-pressure side heat exchanger, and wherein a refrigerant outflow side of the third low-pressure side heat exchanger is connected to the bypass inlet-side connection part.
 10. The refrigeration cycle device according to claim 8, wherein the plurality of low-pressure side heat exchangers further include a third low-pressure side heat exchanger, and wherein a refrigerant outflow side of the third low-pressure side heat exchanger is connected to the second inlet-side connection part of the second flow passage of the inner heat exchanger.
 11. The refrigeration cycle device according to claim 8, wherein the first outlet-side connection part includes two outlet-side connection portions, one of which is connected to a part of the plurality of the decompression units and the other one of which is connected to the other part of the plurality of the decompression units.
 12. The refrigeration cycle device according to claim 8, wherein the inner heat exchanger is a double pipe part in which an inside pipe is passed through an outside pipe, and wherein one of the first flow passage and the second flow passage is a flow passage between the outside pipe and the inside pipe, and another one thereof is a flow passage within the inside pipe.
 13. The refrigeration cycle device according to claim 12, wherein the double pipe part includes one or more bending portion, and wherein a total bending angle of totalizing a bending angle of the bending portion is 160 degrees or more.
 14. The refrigeration cycle device according to claim 12, wherein the double pipe part has a length of 600 mm or more.
 15. The refrigeration cycle device according to claim 12, wherein the first flow passage is a flow passage between the outside pipe and the inside pipe, and wherein the second flow passage is a flow passage within the inside pipe.
 16. The refrigeration cycle device according to claim 8, wherein at least one of the low-pressure side heat exchangers is used for cooling a compartment of a vehicle.
 17. The refrigeration cycle device according to claim 8, wherein refrigerant is HFC134a.
 18. A piping structure for a refrigerant cycle device, comprising: an inner heat exchanger that has a first flow passage in which high-pressure refrigerant before being decompressed flows and a second flow passage in which low-pressure refrigerant after being decompressed flows, the first and second flow passages being provided to exchange heat between the high-pressure refrigerant and the low-pressure refrigerant; and a bypass pipe that defines a bypass flow passage through which a part of the low-pressure refrigerant flows while bypassing the inner heat exchanger. 